Filter old to new references when moving parts of an object.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 507 matching lines @@
         return cell_space();
       case CODE_SPACE:
         return code_space();
       case NEW_SPACE:
       case LO_SPACE:
         UNREACHABLE();
     }
     return NULL;
   }
 
+  void MoveElements(FixedArray* dst, int dst_index, FixedArray* src,

[Michael Starzinger, 2013/01/08 13:13:00]

This method needs a comment explaining it's semantics. Also I would move it down
to the other FixedArray methods (e.g. somewhere around CopyFixedArray).

The assumption is that whenever we move values in an object that "src == dst"
holds. So I think it makes more sence to have an API that just takes one object
pointer, two offsets into it and one length. This also makes further
optimizations easier. WDYT?

[Hannes Payer (out of office), 2013/01/09 09:32:46]

Done.

+                    int src_index, int len);
+
   bool always_allocate() { return always_allocate_scope_depth_ != 0; }
   Address always_allocate_scope_depth_address() {
     return reinterpret_cast<Address>(&always_allocate_scope_depth_);
   }
   bool linear_allocation() {
     return linear_allocation_scope_depth_ != 0;
   }
 
   Address* NewSpaceAllocationTopAddress() {
     return new_space_.allocation_top_address();
@@ skipping 2303 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_